The dog should be able to stand up and turn around easily inside his/her crate. I even give them a little extra room!

 

As long as the dog can stand up and turn around comfortably, that should be great.

 

Our crate is big enough for both our dogs. They say the idea is not to get a crate too big for the dog to poop in one corner and sleep in another, but our dogs don't do well in a tiny crate. We don't have too many problems with them having accidents in the crate unless they are kept in them too long.

 

That sounds like the dimensions for our crate. Medium sized?
It's worked great for us size-wise.
You definitely don't want it to be too big, especially if you're still housetraining.